The Leye carbonate platform in northwest Guangxi is a typical Paleozoic isolated carbonate platform in the northern part of the Youjiang Basin. The Upper Paleozoic in this platform consists almost completely of shallow water carbonates with a thickness of up to 3 000m，without significant terrestrial influx，and is in sharp contrast with the contemporary diversified facies of sediments on the shallow shelf in the north and with the deepwater chertargillaceous sediment assemblages in the surrounding areas. In this platform，two major facies types，the reefrelated grainstonepackstone assemblage along the margins and the wackestonemudstone assemblage in the backreef lagoon，can be recognized for the Upper Paleozoic. The architectures of the depositional sequences and the sedimentary characteristics of the Upper Paleozoic are mainly controlled by the base subsidence，sealevel eustacy and climate changes，along with the change of the carbonate production rate in the basin. The current study shows that the Leye platform was initially formed as a microterrane that was split from the southern margin of the Yangtze Platform and gradually slipped into the basin as intensive expansion and subsidence occurred in the Youjiang Basin in the Late Devonian. The Leye platform had experienced three stages in evolution during the Late Paleozoic: 1)a marginal carbonate platform(Early to Middle Devonian); 2)an isolated carbonate platform(Late Devonian to Middle Permian); and 3)a drowned carbonate platform(Late Permian to Early Triassic)，with the second stage being most prominent. This probably implies that during the Late Paleozoic, the Youjiang Basin had evolved from rifting to a small oceanic basin with intensive expansion and subsidence，while the southern margin of the Yangtze Platform experienced extension and breaking splitting. The formation and evolution of the Leye platform may have general significance and the suggested model may also be used for other isolated carbonate platforms in the northern part of the Youjiang Basin.